This invention relates to printer wire for printer wire assemblies used in dot matrix printers, and more particularly relates to an improved copper-covered printer wire, and to assemblies thereof, and to a method for producing them.
Dot matrix printers have the capability of high speed printing, useful, for example, in producing computer print-outs. Characters such as letters and numerals are formed by an array of dots printed on the print-out sheet by selective electronic activation of an array of printer wires.
The printer wires are fabricated from an impact and wear-resistant material such as tungsten, tungstenrhenium alloy or tungsten carbide, and each is supported by a steel pin or armature, the pin or armature defining a hole or socket for receiving a base portion of the wire. One method of forming the wire-pin assembly involves drilling a hole through the steel pin to accomodate a base portion of the wire and then enlarging a portion of the hole to accommodate a braze preform. The wire and braze preform are then inserted into the pin from opposite sides. Brazing is accomplished by induction heating the assembly to melt the braze and allow it to flow between the wire and hole wall.
A disadvantage of this method is that use of a through hole leads to the impact of printing being entirely absorbed by the braze. It is also difficult to fixture the assembly for brazing, since the pin, wire and braze preform must all be maintained in the proper relative positions by the fixture.
A problem encountered in the use of tungsten printer wire is that the brazing operation tends to lead to wire embrittlement, and consequent premature failure of wire assemblies during printing.